Antimicrobial treatment of organic materials and composition therefor



United States Patent ECRQBEAL TREATMENT OF @RGANZC MATERIALS AND CGMPUSiTEGN THEREFGR Meyer Mendelsohn, New York, and Carl Horowitz,

Brooklyn, N21, assignors, by mesnc assignments, to

Yardney International Corp, New York, N.Y., a corporation of New York No Drawing. Filed Dec. 11, $59, Ser. No. 858,871

11 Claims. (Ci. 8-1155) The present invention relates toa treatment of textiles and textile fibers of natural or synthetic origin, cellulosic or plastic resinous sheets, and similar organic materials in a manner imparting to them antimicrobial properties. This application is a continuation-in-part of our applications Ser. No. 548,253, filed November 21, 1955, Ser. No. 738,697, filed June 2, 1958, and Ser. No. 760,857, filed September 15, 1958, all now abandoned.

It is known that zinc and certain of its compounds are highly active against a wide spectrum of micro-organism. Heretofore, however, it has been difficult to utilize this property in industrial processes such as the manufacture of paper, textiles and the like where the presence of substantial quantities of free Zinc or zinc oxide would be objectionable and where, up to now, no practical way had existed for maintaining a small percentage of zinc firmly attached to the material so as to retain its effectiveness during normal use, washings and so forth.

An object of the invention is to provide a process for virtually permanently fixing a small quantity of zinc in the molecular structure of cellulosic, proteinaceous and other organic materials such as, for example, wood, paper, cotton, linen, rayon, wool, silk natural bristles, hides, cellulosic sheets and films, sponges casein fibers and films, gelatin in foam or film form, and various thermoplastic resin such as polyamide (e.g. nylon) and polyester fibers and sheets.

Another object of the invention is to provide a novel chemical composition for use in such process.

It is also an obiect of the invention to provide a treatment for the purpose described which can be carried out at only moderately elevated bath temperatures, thus enabling the processing of heat-sensitive fabrics and the like.

A further object is to provide, as a novel industrial product, an article of commerce made of one or more of the aforedescribed organic materials and treated in such manner as to be resistant to micro-organisms without being toxic or irritating to humans.

It is known to treat cotton fibers with a solution of urea and a zincate of sodium or potassium for the purpose of reducing shrinkage. In this known process, operating under conditions of very high alkalinity, the zinc compound remains in contact with the fabric for only a short period and is then washed out. The process of the present invention takes place in a considerably less alkaline or slightly acidic medium and, while employing urea or some other source of amine groups as a fixing agent, utilizes the presence of a sequestrant or chelating agent to form a zinc complex which is readily taken up by the molecule of the organic material to be treated.

The process according to the invention, accordingly, involves the steps of mixing together a water-soluble zinc salt, a chelating agent and an aminating agent and forming from this mixture an aqueous solution in which the organic material to be treated may be immersed until 'the molecules have taken up the zinc sequestrant complex.

3,079,213 Patented F eb. 26, 1963 The organic materials so treated are rendered resistant to bacteria so as not only to be safe from destruction by such organisms but also to be no longer a carrier of disease-bearing microbes. Frequently, the treated materials also appear resistant to mildew-causing organisms and have improved physical strength. Finished garments or similar industrial articles may be treated as well as fibers and fabrics.

While it has been known in the past to coat various materials with antimicrobic substances, such coatings have had several severe drawbacks including toxicity, allergenicity, and dye-destructiveness. Various forms of iodine, mercury, and organo-halides have proved to be either fugitive, toxic or prone upon repeated use to cause a high incidence of allergic reaction. Moreover, each of the above has aifected either the dye structure or the substantiveness of the base material to dyes. with such types of materials have been noted to dye with difliculty, and often not at all, to fade with time, or to change hue when exposed to actinic rays. In contrast, the compounds of this invention are formed within the polymeric chain and are, therefore, an integral part er the structure of the polymeric material. Moreover, since the treatment adds reactive groups to the molecule, it has been noted that the polymeric organic materials thus modified dye with ease and the colors are at least as intense as those achieved in the untreated fabrics.

An important advantage of the process of the invention is that since the active complex is in chemical combination with and directly incorporated into the polymeric structure, it resists removal from the polymeric material. It has been found that fabrics so treated retain their antimicrobic properties despite repeated washings. In fact, improved physical properties of the fabric as -a result of this treatment permit it still to exert antimicrobial effects after a number of washings suflicient to weaken and disintegrate untreated control fabrics. At the Sametime, the treatment of this invention does not detrimentally affect such physical properties of cloth, fibers and sheet material as smoothness, flexibility, softness. in hand, washability and wettability.

For treating articles under near-neutral or acidic conditions, boric acid, borax, alkali-metal acetates (e.g. the acetates of sodium, potassium or lithium) and other common buffering agents as well as mixtures thereof are advantageously added. Any of the commercially available textile surfaotants of the ionic, especially quaternary, or non-ionic types will serve as the wetting agent or detergent, including, for example, the various sulfonated long-chain alcohols and esters as well as phenolates, sorbates, quaternary ammonium salts or naphthenates. The use of quaternary ammonium salts has been found to be especially advantageous in the treatment of nylon. The following compounds are illustrative of the detergents which may be employed:

TABLE A Non-Ionic Detergents Nonyl phenoxy polyloxyethylene ethanol (Igepal CO 633) Polyoxyethylene sorbitol stearate (Morosol SL) Polyoxyethylene stearate (Myrj 45) Fabrics treated,

Alkyl (fatty acid) sbenzyl dimethyl ammonium chloride benzalkonium chloride) Tallow trimethyl ammonium chloride (Arquad-T) SQYB- 'trimethylammonium chloride (ArquacFS) D ode,cyl trim'ethyl ammonium chloride (Arquad 12) llepresentativ Ut Tr th ncl mine A i ne rpp'yla me- Toluidine E y m t p rEhcnylene-diamine Mb hc i 1 Melan initial mixtureof zinc. salt, seguestrant, bufiering agent and detergent (with or 'withoutaminating agent) which. can itselfserve as an. article'of commerce, may

ire-prepared either in dryv granulated form or as a liquid concentrate. 1T0 manufacture the Ffo'rrn'er,"'the dry ingredients are mixed together and granulated'inknown manner. To form thertreatmentbath, a requisite amount of; the granulated product is dissolved whereupon 'the liquid concentrate maybe dilutedtoa desired extent. The bath is hroughtto an elevated tmeperature' and the mate rial to beftre'ated isdm'mersed in it. The proportion of; concentrate in the bath depends on the amount of zincamine complex 'itis desiredto incorporate into the final product. In general, a good matters to utilize'from 0.5%; to by Weightof the concentrate in the treat ing.'-bath to "obtain optimii m'result's, "1% to about 10% beingrprfeferrd: w

Eurther control of the deposition of the zinc-amine polymer in the fibermay beeffectuated by the degree of; wettingrand the curing temperature used to fix the complex in theifibers. A rncasure'of the degree of wetting andipenetration'bf the reactants is the pick-up of bath liquid by'thefi bers. Tnis pick-up is defined as the percentile cithe difference between'wet and dry weights to theedryfweight 'of the'fibers. The greater the degree ofpick ilp the lower the necessary initial concentration of the"complexing 'agent. Generally, higher fixing tempera turcs result in a firmer bonding ofthe zinc complex to the polymeric molecule Ofjlhfiif3ld material.

It has further been determined that the process and the baths used therein are compatible with the various wash and wear treatments presently applied to textiles. These lgnown treatments consist in the impregnation of the textile with polymeric resinous materials of either the thermoplasticor the thermosetting type. The thermoplastic treatinent resins are uspally applied in the form of emulsions, while the; thermosetting-type materials are applied form of, aqueous solutions of the resin pre poly'fiiers which are subsequently set in the fabric by the applicationtot heat Theftraitmentof this invention can teaser-ea out "before or during'the application of the Wash, n ofreither't'rea The single-step process oi treatment according to V treatment without loss in etiectiveness invention is most efiiciently practiced in aqueous baths with the va io s comp nen pre n in th nl owiae concentrations:

Percent Chelating agent or sequestrant 0.1 to 10 Water-soluble organic or inorganic zinc salt 0.5 to 50 Aminating agent 0.5 to 30 Detergent or'wetting agent '0 to 15 Buffering agent 0 to 25 If the invention is to be practiced as a two-step process, a granulated mixture comprising the soluble zinc .Salt, a detergent and a sequestrant is advantageously prepared for dissolution in an aqueous medium constituting a first treating bath; next, a second aqueous bath comprising from 015% to 30% of the above-mentioned aminating or fining agent isproduced. In general, the reactive proportions of the ingredients of the granulated mixture introduced intothe first bath may'vary, in the dry state,

within the following ranges:

Percent Zinc salt 20-90 Sequestrant 2-30- Deter-genr"; f 030 Buffering agent 0-40 For optimum antimicrobial action, however, it is found that thepreferred ranges 'a'reapproximately 50% 70% for. the zinc salt, 2.5,%1 0% fonth e sequestrant,'3-10% for the detergent and 15 70-33% for the buffering agent.

"In many. instances, it will be found desirable to invert theorderfof the two baths listed above, by first pretreat ing the fabric or other. organic or fiber material with the aminating agent and subsequently immersing said material, while still wet, in the active zinc-containing bathcomposed as indicated above.

"lilore'specific modes or operation will be described infthe following examples. It is to be noted that the enamplesonly represent preferred modes with regard tol'the specific material set forth. Departures from the specific formulations may be necessitated by changes in the material to be treated, time or temperature. Unless otherwise specified, the parts given are by weight.

EXAMPLE 1 [Additive A] Parts Tetra-sodium salt of ethylene diamine tetra-acetic acid (E.DZT.'A.) -Q 1 Zinc chloride 22 Sodium'acetate Boric acid 1* Ethylene cy'cloimido, l alkyl (fatty acid), 2 hydroxy ethylene sodium alcoholate, methylene sodium carI- boa'ylatc (Miranol CM concentrate) 2 Urea? Q; L 3i Thirty grams ofthe above mixture is dissolved in a liter of; water to form'the treatment bath. Thebathis heatedto 70- C. and knitted cotton socks are immersed in the hathfor lOminutes and then extracted, rinsedin water and; dried. Tests indicate that contact with the treated socks inhibits; growth of test bacteria. More over this inhibiting quality continues in the socks even after theyv have beensubjected to as many. as fifty-automatic-washingmachine cycles, Untreated control socks, do not display any inhibiting properties, yet it is noted that 29% of the controls showed tearsw due. to the wear resulting from this washing procedure alone. Treatedsocks do not tear.

Similar results are obtained when zinc acetate is employecl in lieu of zinc chloride. to formulate the additive according to Example I.

' EXAMPLE 2 in'the wash and wear treatmentof cotton fabrics, and

the mixture is agitated until the additive is completely dissolved therein.

The fabric to be treated (shirting) is immersed in the resulting solution at room temperature, until it is completely wetted (30-60 seconds), and is then removed from the bath. The fabric is drained or pressed until the pick-up of the bath by the fabric is 70%l20'%. The fabric is then dried at, for example, 120 C. for one minute and Washed in a softening bath containing a detergent such as, for instance, polyglycol monolaurate or monostearate. Tests show inhibition of bacterial growth by contact with the treated fabric. erty of the treated material is observed after the treated fabric is subjected to 50 Washing cycles in standard soaps. Untreated controls possess no inhibitory properties either before or after the washing cycles. Similarly, shirtings treated with the wash and wear resins without the additive are found to have no anti-bacterial properties.

EXAMPLE 3 [Additive B] Fifteen grams of additive B are dissolved in a liter of water, at 70 C. Woolen socks are immersed in the solution until they absorb 90 to 120% of their weight of the solution. The socks are then heated to 50 C. and maintained at or above that temperature for at least minutes or until the socks are dry. The residue of the bath is then washed or rinsed from the socks. The so treated socks maintain their anti-microbic properties through washing cycles. Controls exhibit no microbeinhibiting characteristics either before or after the washing. When the di-potassium salt of methylimino diacetic acid is substituted for the tetra-sodium salt of ethylene diamine tetraacetic acid, similar results are observed.

EXAL'IPLE 4 A bath according to Example 3 is used for the processing of cotton-polyester (Dacron) 65-35 shirting. The shitting is immersed for 2 minutes in the bath at C. until the dry-Weight pick-up of the bath by the shirting is 70%. The fabric is then dried at 80 C. The finished fabric (after rinsing and drying) inhibits growth of bacteria in direct contact with it before and after 40 wash cycles.

EXAMPLE 5 Rayon tricot fabric is treated in the manner set forth in Example 3 except that the fixing and drying is carried out between and 80. The fabric exhibits bacteriainhibiting properties before and after 30 wash cycles.

The following examples illustrate the two-step treatment according to the present invention:

EXAMPLE 6 Parts Tetra-sodium salt of ethylenediamine tetraacetic acid 1 Miranol CM concentrate (cf. Example 1) 2 Sodium acetate 5 Boric acid 1 Zinc chloride 22 This propin the bath and the pick-up rate. Such materials, without further fixing, retain their antimicrobial properties up to approximately 10 washings.

EXAMPLE 7 The products of Example 6, having a zinc content of 3%, are fixed by immersion in a 2 /2% solution of urea at C. for 5 minutes. A specific product so treated, hospital sheeting, maintains its antimicrobial properties after 50 washings against common skin bacteria as shown by inhibition zones in the standard agar Petri-dish test.

EXAMPLE 8 The products of Example 6, having a 2% zinc content, are med by immersion, for 7 minutes at 65 C. in a bath containing 3% monoethanolamine. Handkerchiefs treated in this manner maintained their antimicrobic properties over periods of prolonged use and many washings.

In lieu of monoethanolamine, morpholine can also be used as the aminating agent.

EXAMPLE 9 Parts Tetra-sodium salt of E.D.T.A. 1 Polyoxyethylene sorbitol stearate 1 Sodium acetate 5 Borax (tetrasodium borate) 2 Zinc chloride 10 The above mixture granulates easily by the interchange of the water of crystallization between the borax and the zinc chloride. One part of the above mixture dissolved in 9 parts of Water yields a protein-treating bath, having a pH of approximately 8. A proteinaceous material, such as wool, silk, leather, or catgut sutures, when immersed in the above treatment bath for preferably not less than 10 minutes absorbs Within the protein molecule up to 4% of zinc. The zinc may be fixed permanently within the molecule by any of the fixing baths mentioned in connection with the cellulosic materials (Examples 7 and 8) with similar antimicrobial results. It should be noted that proteins are preferably treated at lower temperatures but for longer treatment times. Woolen fabrics after 13 minutes in the above treating solution at 65 C. have a zinc content in excess of 1% fixed within the fabric. Moreover it has been noted that dyed treated fabrics possess greater resistance to actinic rays than the same dyed fabrics without said treatment.

EXAMPLE 10 Cellulosic materials as mentioned in Example 6 or proteinaceous materials as set forth in Example 9 are first immersed for 5 minutes in a urea solution as mentioned in Example 7. This treatment is immediately followed by immersion in a bath as described in Example 6. The wash resistance of the treated material is at least equal to that of the product of Example 7.

The process of Example 10 may be modified by substitution of the ingredients of Example 8 and/ or 9 for those listed in Examples 6 and 7.

The presence of chelating agent appears to have the dual efifect of facilitating the introduction of the zinc into the molecules of the organic base material and detoxicating the resultant product by rendering harmless any excess zinc salts which might otherwise be left in contact therewith.

The use of a two-step process for the treatment according to the present invention has the advantage of appreciably shortening the time during which the material to be treated will remain immersed. Thus, immersion times of as little as a few seconds per bath have been found suitable in many instances, in contradistinction to an immersion time upwards of approximately five minutes for the sole bath of the one-step process. It may also be mentioned that the time interval elapsing between the successive immersions of the two-step process is not critical and may range from about a second to .a weel: or longer, any iijte'rvening dryingof the. treated material being of no ap? parent consequence regardless of the order in which the two steps are applied. Thus, the two-step treatment lends itself particularly for use incommercial processing plants, Where long webs of fabric or :the like could be treated in are-continuous operation or wherelpiece goods could be im mersed in baths for short periods, whereas the one-step treatment will be preferable for small laundries and home washing machines.

We have found. that, for reasons not fully understood, bath compositions including a combination of two detergents, one from the non-ionic group and the other fromthe quaternary group of Table A, are particularly effective if' the treatment is to be applied to films or fibers not readily wettable in aqueous solution, such as polyamides (nylon); The foregoing examples may, accordingly, be modified for such purposes by replacing a fraction (preferably one-half) of the detergent of one type by a like amount of detergent of the other type.

Whereas the treatment previously described is most expeditiously carried out at immersion temperatures ranging between 60 C. and 100 (3., followed (if desired) by a forceddrying at evenhigher temperatures if the treated material can, be safely subjected thereto, we have found that, in accordance with. a further feature. of the invention, the process. can be. performed at considerably lower tempcnatures (upwards of about 45 C.) if a smallpercentage of a natural or synthetic gum is admixed with the active bath. This class of additives includes polyvinyl alcohol; water-soluble polyuronic acids and derivatives thereof, such as alginic or pectinic acid and their sodium or potassium salts;. and water-soluble cellulose ethers such as methyl cellulose, carboxymethyl cellulose or hydroxyethyl cellulose.

The quantity of temperature-lowering additive (gum) may se u rd o a u %..br W h of h o i s; the upper limit is given by the proportion which will'tend tornake the bath too viscous for effective immersion of the article to, be treated, such proportion being generally in the vicinity of '5 of the liquid or up to. about 50% of the. solids, depending upon the total ratio of solids to liquid whichm ay range between 0.1% and 25% but is preferably held within the limits of 1%. and 1.0%, by weight.

EXAMPLE- 11 The composition of Example. 1 (additive A), is supplemented by parts of polyvinyl-alcohol powder. Cotton goods (e.g. socks) are immersed for ten minutes as specified above, but at atemperature of 50 C. The treatment is, otherwise the same. as, that previously described, with closely similar results.

Inlikemanner the compositions of the treatment bath) the number .of permissible washings is increased by this addition, on the average, by 20 to 30%.

The preferred pH for the active bath of the two-step processorthe combined ,bath of the one-step process according to the invention ranges substantially between 5 and 7. The extended operative range of the pH is from 3 to 9. Alkaline solutions with a pH greater than 10 should be avoided.

We claim:

1. An antimicrobial composition comprising a zinc salt, an aminating agent and a chelating agent.

2, A composition according to claim 1 including a bufiering agent. a

'3. A composition according to claim 1 including a wetting agent.

4. An antimicrobial composition comprising a zinc salt selected from the group consisting of zinc chloride,- zinc bromide, zinc nitrate, zinc sulfate and zinc acetate; urea; and an alkali metal salt of ethylenediaminetetraacetic acid.

5. As an article of manufacture, textile fiber impregmated with a composition comprising a zinc salt, an aminating agent and a chelating agent.

6. An article of manufacture according to claim 5 wherein. said textile fiber is selected from the group consisting of cellulosic, proteinaceous, nylon and polyester fibers.

7. A composition of matter comprising from .5% to by weight of a water-soluble zinc salt, .l% to 10% by weight of a chelating agent and from .5% to 30% by weight of an aminating agent.

8. A composition of matter according to claim 7 containing up to 15% by weight of a surfactant.

9. An antimicrobial composition comprising zinc chloride, tctraalkali metal salt of ethylenediaminetetraacetic acid. and urea.

10. A process for imparting antimicrobial properties to textile fibers comprising applying in solution to said subjecting the fibers so treated to the action of an aminating agent whereby antimicrobial properties are imparted to said textile fibers.

7 References Gited in the file of this patent UNITED STATES PATENTS 2,304,478 Rosenzweig Dec. 8, 1942 2,396,514 Kreidl et a1 Mar. 12, 1946 2,459,896 Schwarz Jan. 25, 1949 2,459,897 Schwarz Jan. 25, 1949 2,525,049 Signaigo c Oct. 10, 1950 2,527,141 Mantell et al. Oct. 24, 1950 2,572,923 Gaver et a1 Oct. 30, 1951 2,609,368 Gaver Sept. 2 1952 2,648,593 Stanton et al. Aug. 11, 1953 2,671,779 Gaver et al. Mar. 9, 1954 2,868,724 Zech Jan. 13, 1959 2,904,468 Davis et al. Sept. 15, 1959 

10. A PROCESS FOR IMPARTING ANTIMICROBIAL PROPERTIES TO TEXTILE FIBERS COMPRISING APPLYING IN SOLUTION TO SAID FIBERS A ZINC SALT, AN AMINATING AGENT AND A CHELATING AGENT WHEREBY ANTIMICROBIAL PROPERTIES ARE IMPARTED TO SAID TEXTILE FIBERS. 